Electrolytic cell



Feb- 3, 1.959 w. HONSBERG 2,872,403

ELECTROLYTIC CELL Filed Feb. 1, 195e I N VEN TOR:

WERBIYNER HONSBERG i migrar ATTYS United States Patent@ ELECTROLYTICICELL Werner Housberg, Ludwigshafen (Rhine), Germany, assignor toBadische Anilin- & Soda-Fabrik Aktiengesellschaft, Ludwigshafen (Rhine),Germany Application February 1, 1956, Serial No. 562,895 Claimspriority, application Germany February 3, 1955 Claims. ('Cl. 2041-220)This invention relates to an electrolytic cell, and more particularly tothe type of cell in which a fluid cathode is adapted to flow in aninclined trough receptacle.

Cells of this type are particularly suitable for the electrolysis ofalkali chhiride solutions wherein flowing mercury is used as thecathode. Such cells usually include a primary unit in which bydecomposition of the electrolyte the mercury is laden with alkali metalby the formation of an amalgam, and a secondary unit, often termed thedenuder, in which the alkali metal is separated from the mercury. Theprimary unit of such an alkali metal chloride cell with a horizontallydisposed iowing mercury amalgam cathode usually consists of a lower partwhich is constructed as a trough to give the circulating mercury amalgama definite guidance, and an upper part which serves as a cover for thelower part. On the bottom of the lower part or trough, which is usuallyprovided with a slight longitudinal gradient amounting to about 2%, themercury or amalgam iiows as a thin band. This band should be spread outas thinly as possible in order to limit the amount of mercury requiredto a minimum, and, on the other hand, it should be spread out to thegreatest possible width because the output of the electrolyzer dependson the Width of the band. However, it is a prerequisite for anunobjectionable conduction of the electrolysis that the band shouldcover uninterruptedly the bottom of the trough, which lis ordinarilyconstructed wholly or partly as an iron cathode, and is not disconnectedor otherwise interrupted. For this reason the bottom should not exhibitany unevenness, should have a constant gradient throughout the wholelength of the support viewed in the direction of ow, and should behorizontal at all points when viewed in a direction laterallyperpendicular to the ilow.

4These conditions can be initially fullled without appreciablediliiculty when the mercury band is not wider than about 80 centimetersand not longer than about 8 to 9 meters. A suitable cell trough for sucha case consists in a known construction of a rolled iron beam having aU-shaped cross-section as in a channel beam or an I-shaped cross-sectionas in an I-beam, such that the web of the beam forms the bottom and theflanges form the sides of the trough. Since such rolled beams, which aremounted on two base support points, must be free from sagging andtwisting and remain so, rolled sections of considerable thickness arenecessary; for example, with a rolled iron beam of I-shapedcross-section having a width of SO centimeters, the thickness of theflanges and web amounts to 30 millimeters. Apart from this, rolled beamshaving a Width of more than 8O centimeters are not economical toproduce.

For the construction of large cells, it has therefore been proposed touse flat sections welded together from sheet metal in a box-like orhollow construction. It is difcult, however, to prepare cell troughs ofthis type which are free from strain. The cells mounted at roomtemperature become distorted at the high operating temfirice peratures,thereby seriously disrupting the uniform ow of the mercury band.Internal strains of the material caused by welding during preparationcannot subsequently be removed, particularly where the trough is linedwith hard rubber. ln order. to avoid these difficulties which arise fromthe welding process during preparation, it has been proposed to make thecell trough by screwing together individual parts, for example, byscrewing onto a sheet metal plate which serves as the bottom of thetrough of the cell, while using rubber seals, a U-section iron framewhich forms the walls of the trough. These rubber seals, which are underthe pressure of the mercury, can only with difficulty be prevented fromleaking at the varying temperatures at which the electrolyzer isoperated.

One object of the present invention is to provide an electrolytic cellfor a liowing fluid cathode in which unevenness in the surface overwhich the fluid s spread can be corrected.

Another object of the invention is to provide an electrolytic cell for aliuid cathode adapted to ow in an inclined trough receptacle in whichunevenness in the bottom of the trough caused by stresses in thematerial the trough consists of, which stresses becoming' eiective athigh operating temperatures, can be corrected even while the cell is inoperation.

Another object of the invention is to provide an electrolytic cell for auid cathode adapted to flow in an inclined trough receptacle wherein thetrough can be constructed of a single, continuous, integral sheetmaterial which is relatively llat, thin and flexible.

Still another object of the invention is to provide an electrolytic cellfor a flowing fluid cathode which is easily and economically constructedwhile overcoming the various disadvantages of prior cells set forthabove.

These and other objects and advantages of the invention will be moreclearly understood upon a consideration of the following descriptiontaken in conjunction with the accompanying drawings wherein similarreference figures are employed to designate similar parts in all of thefigures, and in which:

Fig. l is a side elevational View, partly in cross-section, of anelectrolytic cell constructed in accordance with the invention;

Fig. 2 is an enlarged cross-sectional view of the same taken on the line2 2 of Fig. l with some parts omitted; and

Fig. 3 is a side view, partly in cross-section on the line 3-3 of Fig.2.

According to the present invention, the bottom of the trough isconstructed of a at, flexible material, for example, such as can bepressed from sheet metal or made from plastic. Suitable materials forthe construction of the trough include sheet iron, sheet aluminium andplastics such as polyvinylchloride and other polymers which areresistant to attacks of elevated temperatures and chemicals under theoperating conditions. The thickness of the material can vary from assmall as a few millimeters, where sheet iron is'employed, to any desiredthickness depending upon the relative flexibility of the materialemployed.

The bottom of the trough is arranged on a plurality of supports spacedintermediately the ends of the trough. The height of each support isindividually adjustable so as to remove unevenness in the bottom whichmay occur, for example, during erection or in operation of the cell. Thetrough may therefore be formed from a unitary thin sheet of any desiredsize, and it is no longer necessary to have to resort to a weldingmethod for the assembly of the trough from several individual parts, sothat internal straining of the sheet and the other diiculties mentionedabove cannot occur.

The variability in the height of the supports can easily be ensured bysubdividing cylindrical supports, providing the two parts withscrewthreads and connecting them by a threaded sleeve, thereby providinga turnbuckle supporting means. Then, by rotation of the threaded sleeve,a lengthening or shortening or" the support can readily be effected atwill and local unevenness, i. e. depressions or `protuberances in thebottom of the trough whichimpair the uniform ow of the mercury band,thereby removed. These corrections can readily be carried out duringoperation of the cell. Instead of a turn- `buckle, any other means canbe used which make possible an adjustment of the height of the supports.

It is advantageous to mount all the supports on a commonbearing member,e. g., a rod which is arranged inl about the same vertical plane as thelongitudinal of the trough and which is separated from the base byinsulators. Also, a tube has been found to be suitable as the bearingmember with the lower ends of the supports secured to the wall of thetube.

A tubular bearing member can serve at the same time with advantage asthe denuder, i. e. the vessel for the regeneration of the mercuryleaving the cell. ln the electrolysis of alkali chloride solutions bythe mercuryamalgam method, the tube would therefore be constructed asthe secondary cell for the decomposition of the mercury amalgam.

Referring now to the drawings, a mercury cell for the electrolysis of analkali chloride solution is illustrated in which a primary unit for thedecomposition of the electrolyte includes a trough l pressed from asingle sheet of iron to form a bottom 2. and sides 3. The trough bottom2 measures about 15G centimeters in width and 1500 centimeters inlength, with a thickness of 0.4 centimeter. The bottom of the trough isinclined downwardly from left to right with a gradient of about 2%. Acover 4 is provided to enclose the trough, a plurality of graphiteelectrodes 5 being inserted through the cover to act as the anode in theelectrolytic solution contained in the trough. rlfhe cathode for thecell is mercury (Hg) which ows as a thin band on the trough bottom 2 inthe direction of the arrow, i. e. from left toi-ight in the primaryunit. Current is carried from the flowing mercury cathode by the troughitself when constructed of a conducting material such as sheet iron andin the case of a non-conducting material such as a plastic or the like,by contact plates consisting of a conducting material which are localconstituents of the bottom.

The secondary unit or denuder is formed as a tube 6, its axis falling inthe same vertical plane as the axis of the primary unit or trough. Thetube 6 is inclined from right to left so that the mercury amalgam formedin the primary unit is caused to flow in the direction of the arrow asshown. Thus, mercury flows down the trough 1 into a collecting member 7,then ilows in the opposite direction through the tube 6 where theamalgam is decomposed, and the regenerated mercury is returned to theprimary unit or trough by means of a pump t; driven by a motor 9. Thetube 6 is supported by brackets l0 mounted upon insulators lll whichseparates the apparatus from the base pedestal l2 in order to preventgrounding of electrical current.

In order to correct unevenness in the trough bottom 2 caused by theconstruction or erection or vthe trough or by higher operatingtemperatures, a plurality of paired support assemblies 13 are shown inFig. l to :be spaced intermediately the ends of the trough. The distancebetween each pair of support assemblies is governed to a certain extentby the weight and flexibility of the material used in constructing thetrough. ln the continuous beam structure shown, a distance of about 40centimeters was provided between each pair of supports to preventexcessive longitudinal deflection.

The pair of support assemblies 13 are connected at their top end to thetrough bottom 2 and converge downwardly to be mounted upon the tubebearing member 6. Figs; 2 and 3 more clearly illustrate the constructionof each pair of supports. Thus, the trough .bottom 2 is attached to anupper threaded rod 14 by a free pin connection l5 in a trough connectingplate i6. A lower threaded rod 17 is secured by a free pin connection 18in a tube connecting plate 19 on the wall of the tube bearing member 6.A threaded sleeve 20 is threadably connected to the upper and lower rodslo and lf to provide a turnbuckle supporting means so that rotation ofthe sleeve in one direction causes the supporting assembly to elongatewhile rotation in the opposite direction causes the supporting assemblyto shorten. The trough connecting plates i6 are securely attached to thetrough bottom by pins. Welding of the trough connecting plates to asheet metal is not advisable since the deformation caused by weldingwould be dicult to correct. The trough connecting plates 16 are spacedinwardly from the edges of the trough and a distance provided betweeneach plate such that excessive horizontal deilection caused by theweight and flexibility of the sheet material itself is prevented.

Prior to operation of the cell, local areas of unevenness in the bottomof the trough can be readily observed and corrected by adjusting theheight of the individual supports. During operation of the cell,unevenness in the bottom of the trough can be detected by means ofopenings in the cover 4 (not shown in the drawings) and ofperiscope-like observing devices inserted in said openings, andcorrespondingly corrected by adjusting the height of the supports. Bymaintaining the even distribution of mercury over the trough bottomthroughout the continuous operation of the cell, a more eicient outputis provided while eliminating costly shutdowns.

What I claim is:

l. In an electrolytic cell in which a lluid cathode ows in a thin bandcovering the bottom surface of an elongated, inclined trough receptacle,the improvement which comprises: an elongated trough consistingessentially of a unitary, flat, thin, flexible bottom and side wallsintegral with said bottom, the weight exerted by and the relativeflexibility of said bottom resulting in a normally excessive deilectionthereof over an unsupported length corresponding to less than one-thirdof the total length of said trough, means secured at either end of saidtrough to hold said trough in an inclined plane; a plurality ofindividual adjustable supports spaced intermediately the ends of saidtrough and means at the top end of each support to secure the support tothe ilexible bottom of said trough, the distance between each of saidsupports being Suthciently small to prevent normal excessive deflectionof said exible bottom; and means to individually longitudinally adjustthe height of each of said supports cooperating with said means securingeach support to the bottom of said exible trough for local reciprocalmove ment of the bottom of the trough corresponding to thelongitudinally adjustable movement of the support, in order to correctlocal unevenness in the bottom of the trough.

2. An electrolytic cell as defined in claim l wherein the trough havinga ilat, flexible bottom is constructed from a single thin sheet ofconducting material.

3. An electrolytic cell as dened in claim l wherein the trough having ailat, flexible bottom is constructed from a single thin sheet of iron.

4. An improved electrolytic cell as defined in claim l wherein thelength of said trough is greater than 9 meters.

5. In an electrolytic cell for the electrolysis of au alkali metalchloride solution in which a liquid mercury cathode flows in a thin bandcovering the bottom surface of an elongated, inclined trough receptacle,the improvement which comprises: an elongated trough consistingessentially of a unitary, flat, thin, ilexible bottom and side wallsintegral with said bottom, the weight exerted by 5 and the relativeilexibility of said bottom resulting in a normally excessivelongitudinal deflection thereof over an unsupported length correspondingto less than one-third of the total length of said trough and a normallyexcessive horizontal detlection thereof over an unsupported widthcorresponding to less than one-half of the total width of said trough,means secured at either end of said trough to hold said trough in aninclined plane; a plurality of paired, individually adjustable supportsspaced intermediately the ends of said troughs and means at the top endof each support to secure the support to the flexible bottom of saidtrough, the distance between each of said individual supports beingsuiciently small to prevent normal excessive longitudinal and horizontaldeflection of said exible bottom; and means to individuallylongitudinally adjust the height of each of said supports cooperatingwith said means securing each support to the bottom of said flexibletrough for local reciprocal movement of the bottom of the troughcorresponding to the longitudinally adjustable movement of the support,in order to correct local unevenness in the bottom of the trough.

References Cited in the le of this patent UNITED STATES PATENTS

1. IN AN ELECTROLYTIC CELL IN WHICH A FLUID CATHODE FLOWS IN A THIN BANDCOVERING THE BOTTOM SURFACE OF AN ELONGATED, INCLINED TROUGH RECEPTACLE,THE IMPROVEMENT WHICH COMPRISES: AN ELONGATED TROUGH CONSISTINGESSENTIALLY OF A UNITARY, FLAT, THIN FLEXIBLE BOTTOM AND SIDE WALLSINTEGRAL WITH SAID BOTOM, THE WEIGHT EXERTED BY AND THE RELATIVEFLEXIBILITY OF SAID BOTTOM RESULTING IN A NORMALY EXCESSIVE DEFLECTIONTHEREOF OVER AN UNSUPPORTED LENGTH CORRESPONDING TO LESS THAN ONE-THIRDOF THE TOTAL LENGTH OF SAID TROUGH, MEANS SECURED AT EITHER END OF SAIDTROUGH TO HOLD SAID TROUGH IN AN INCLINED PLANE; A PLURALITY OFINDIVIDUAL ADJUSTABLE SUPPORTS SPACED INTERMEDIATELY THE ENDS OF SAIDTROUGH AND MEANS AT THE TOPEND OF EACH SUPPORT TO SECURE THE SUPPORT TOTHE FLIEXBLE BOTTOM OF SAID TROUGH. THE DISTANCE BETWEEN EACH OF SAIDSUPPORTS BEING SUFFICIENTLY SMALL TO PREVENT EXCESSIVE DEFLECTION OFSAID FLEXIBLE BOTTOM; AND MEANS TO INDIVIDUALLY LONGITUDINALLY ADJUSTTHE HEIGHT OF EACH OF SAID SUPPORTS COOPERATING WITH SAID MEANS SECURINGEACH SUPPORT TO THE BOTTOM OF SAID FLEXIBLE TROUGH FOR LOCAL RECIPROCALMOVEMENT OF THE BOTTTOM OF THE TROUGH CORRESPONDING TO THELONGITUDINALLY ADJUSTABLE MOVEMENT OF THE SUPPORT, IN ORDER TO CORRECTLOCAL UNEVENNESS IN THE BOTTOM OF THE TROUGH.